Two-stage valve suitable as high-flow high-pressure microvalve

ABSTRACT

A two-stage valve for controlling the flow of gas from a pressurized gas supply with an upper main body including a cavity; a lower main body with at least one flow exhaust passage forming a primary flow path through the two-stage valve; a pre-stressed diaphragm sandwiched between the upper and lower main bodies, and pressure control capability for controlling the pressure in the cavity. A secondary flow path exists from the pressurized gas supply through the lower main body, through the upper main body, and terminating in the cavity in the upper main body. A first valve is installed in the secondary flow path to open and close the flow of gas from the pressurized gas supply to the cavity. A second valve installed in an exhaust passage in the upper main body allows the pressure in the cavity to exhaust to the environment. When the second valve is closed, the pressure in the cavity in the upper main body can be increased to lower the pre-stressed diaphragm. Raising and lowering of the pressure in the cavity causes the pre-stressed diaphragm to open and close the flow of gas from the pressurized gas supply through the primary flow path of the two-stage valve. The design of the two-stage valve and its components lends itself to constructing the two-stage valve as a microvalve using Micro-Electro-Mechanical Systems (MEMS) concepts.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to valves for fluids and morespecifically to valves suitable for construction as high flow, highpressure microvalves.

[0002] Small fluid valves are known in the art that have been developedusing Micro-Electro-Mechanical-Systems (MEMS) concepts. These smallscale valves have the advantage of being able to be produced veryprecisely and inexpensively using fabrication techniques more commonlyused in the microelectronics industry. Typically, such valves alsoconsume very low power and have high switching frequencies. While thesevalves have many ingenious configurations, most are limited to lowpressures, e.g., under 200 psig (approximately 1,500 kPa), and all arelimited to extremely low flows, e.g., under 10⁻⁴ kg/second. In fact,none of the actuation mechanisms known, such as electromagnetic,electrostatic, piezoelectric, and shape-memory alloys, are capable bythemselves of producing both the forces necessary to overcome highpressures, and the deflections needed to provide large flow areas.

SUMMARY OF THE INVENTION

[0003] It is an object of this invention to provide a means forswitching high flow rates at high pressures, at the expense of responsetime, by a device that is particularly suitable for fabrication usingmicro-fabrication techniques.

[0004] The present invention is a two-stage valve for controlling theflow of gas from a pressurized gas supply comprising an upper main bodyincluding a cavity therein; a lower main body having at least onepressurized gas supply exhaust outlet passage forming a primary flowpath with the pressurized gas supply; a pre-stressed diaphragmsandwiched between the upper and lower main bodies, the pre-stresseddiaphragm having one side of a portion thereof in fluidic communicationwith the cavity, and the opposite side of the portion thereof in fluidiccommunication with the pressurized gas supply; and pressure controlmeans fluidically coupled to the cavity for controlling the pressure inthe cavity to cause the portion of the pre-stressed diaphragm to openthe flow of gas from the pressurized gas supply through the primary flowpath of the two-stage valve and to cause the portion of the pre-stresseddiaphragm to close the flow of gas from the pressurized gas supplythrough the primary flow path of the two-stage valve.

[0005] The pressure control means comprises the lower main body having asecondary flow path communicating with the pressurized gas supply, theupper main body having a secondary flow path communicating with thesecondary flow path in the lower main body, and communicating with thecavity in the upper main body; a first valve providing (a) an isolatingmeans for isolating the flow of gas from the pressurized gas supply tothe cavity in the upper main body, and (b) an opening means for allowingthe gas from the pressurized gas supply to flow to the cavity in theupper main body, the upper main body having an exhaust passage forfluidically communicating the cavity with an environment at a pressurelower than the pressure of the pressurized gas supply, a second valveinstalled in the exhaust passage, the second valve providing anisolating means for fluidically isolating the cavity in the upper mainbody from the environment, and an opening means for opening the cavityin the upper main body to exhaust to the environment.

[0006] The first valve is installed in one of (a) the secondary flowpath in the lower main body, and (b) the secondary flow path in theupper main body. The lower main body can include a cavity. The lowermain body further can include a boss formed in the cavity of the lowermain body, the boss surrounding a hole acting as the inlet primary flowpath for the flow of gas from the pressurized gas supply, the holefluidically coupled to the opposite side of the portion of thepre-stressed diaphragm. Preferably, the boss formed in the cavity of thelower main body is positioned coincident with the center of the cavityof the lower main body.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 illustrates the two-stage valve of the present invention inthe closed position.

[0008]FIG. 2 illustrates cross-sectional plan view 2-2 of the two-stagevalve of the present invention.

[0009]FIG. 3 illustrates the two-stage valve of the present invention inthe open position.

[0010]FIG. 4 illustrates cross-sectional elevation view 4-4 of thetwo-stage valve of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0011] In FIG. 1, the two-stage valve of the present invention isillustrated. The two-stage valve 100 comprises an upper main body 102which is made typically of one or more laminations of silicon, siliconcarbide, or other suitable material compatible with micro-fabricationtechniques, and a lower main body 104 typically made of one or more ofthe same materials. A cavity 106, hereinafter referred to as the uppercavity 106, is formed in the upper main body 102. Another cavity 108,hereinafter referred to as the lower cavity 108, is formed in the lowermain body 104. The upper main body 102 and the lower main body 104sandwich a diaphragm 110. The diaphragm 110 is pre-loaded so that it isnormally sealed on the boss 112 formed in the middle of the lower mainbody 104.

[0012] A hole 114 through the middle of the boss 112 acts as the inletfor the main flow path. Passages (shown in FIG. 2) are formed in thelower main body 104 parallel to the diaphragm 110 to permit the flow toexhaust when the two-stage valve 100 is opened.

[0013] A secondary flow path 116 is formed in the upper main body 102and the lower main body 104 to connect the side of the diaphragm 110facing the upper main body 102, hereinafter referred to as the upperside of the diaphragm 110 to the high pressure gas supply 118. A firstsmall valve 120 is placed in the secondary flow path 116 to connect anddisconnect the top cavity 106 with the high pressure gas supply 118. Asecond small valve 122 is placed in an exhaust passage 124 on the top ofthe upper main body 102 to provide a means to release high pressure gasto the environment. (Small valve 122 is shown in the closed position inFIG. 1). Both the first and second small valves, 120 and 122, areactuated typically by titanium nickel (TiNi) or piezoelectric actuators,not shown. The entire assembly of the two-stage valve 100 typically ismounted on and attached to a pressure vessel 126 that contains the highpressure gas supply 118.

[0014]FIG. 2 illustrates a cross-sectional plan view 2-2 of thetwo-stage valve of the present invention as illustrated in FIG. 1.Passages 202, 204, 206, and 208, referred to previously, are formed inthe lower main body 104 parallel to the diaphragm 110 to permit the flowto exhaust to thrusters (not shown) when the two-stage valve 100 isopened. Supply gas 118 flows through the center of hole 114 through themiddle of the boss 112 that acts as the inlet for the main flow path andthe secondary flow path 116.

[0015] Referring to FIG. 1, the operations to close the two-stagemicrovalve 100 are as follows. Second small valve 122 is closed to sealthe upper cavity 106 from the atmosphere. First small valve 120 isopened to expose the upper cavity 106 to the high pressure gas supply118, thereby pressurizing the upper side of diaphragm 110. After a shorttime, typically 10 milliseconds or less, both the lower side and theupper side of the diaphragm 110 reach essentially the same pressure asthe high pressure gas supply 118. However, the lower side of thediaphragm 110 will experience slightly lower pressures due to thevelocity of the flow passing through the hole 114 that acts as the inletfor the main flow path. Once the gas pressures are equalized across thediaphragm 110, i.e., the pressure on the upper side of the diaphragm 110equals the pressure on the lower side of the diaphragm 110, the stressesin the pre-loaded diaphragm 110 tend to pull the diaphragm 110 closed onthe boss 112. Once the diaphragm 110 is closed on the boss 112, thepressure on the upper side of the diaphragm 110 acts over the entiresurface area of the upper side of the diaphragm 110 while the pressureon the lower side of the diaphragm 110 acts only over the smaller areaof hole 114 that acts as the inlet for the main flow path. The pressureacting on the center of the diaphragm 110 in the upper cavity 106 is thesame as the high pressure gas supply 118, but the pressure at the lowercavity 108 is lower. This pressure imbalance causes the diaphragm 110 toseal tightly against the boss 112. As a result, the flow of gas throughthe two-stage valve 100 is shut off.

[0016] Referring to FIG. 3, the operations to open the two-stage valve100 are as follows. First small valve 120 is closed, thus isolating thehigh pressure gas supply 118 from the upper cavity 106. Second smallvalve 122 is opened, thus permitting the upper cavity 106 to communicatewith the environment. The high-pressure gas in the upper cavity 106exhausts to the environment, until, after a short time, typically 10milliseconds or less, the pressure in the upper cavity 106 approachesthe pressure of the environment. In the meantime, the high pressure ofthe high-pressure gas at the hole 114 that acts as the inlet for themain flow path starts to force the diaphragm 110 to lift upwards towardsthe upper cavity 106 and away from the boss 112, thereby permitting thehigh-pressure gas to flow through the hole 114 that acts as the inletfor the main flow path, and the high-pressure gas then flows in theradial direction away from the hole 114 at the center of the lower mainbody 104, and parallel to the diaphragm 110, through the passages 202,204, 206, and 208 to the thrusters (not shown).

[0017]FIG. 4 illustrates a side elevation view of the two-stage valve100. The upper main body 102 and the lower main body 104 sandwich thediaphragm 110. The exhaust passages 202 and 206 are illustrated aschannels permitting the high pressure gas supply 118 to exhaust to theenvironment. The entire assembly of the two-stage valve 100 isillustrated as mounted on and attached to the pressure vessel 126 thatcontains the high pressure gas supply 118.

[0018] Those skilled in the art will recognize that the two-stage valvecan be designed for essentially any size application. Furthermore,although the two-stage valve is illustrated with the upper main body inthe upper position and the lower main body in the lower position, thoseskilled in the art will recognize that the two-stage valve can bepositioned in any orientation. When designed as a microvalve, thetwo-stage valve overcomes the inherent lack of force in conventionalactuation technologies by tapping the high potential energy inherent inthe high pressure gas supply. The diaphragm 110 is made preferably oftitanium. The actuators for the first and second small valves 120 and122, respectively, preferably are made of titanium nickel (TiNi) orpiezoelectric and can have small dimensions and small throws (valveoperation distance parameters). Such requirements are consistent withpiezoelectric and shape memory alloy requirements. The first and secondsmall valves switch a small secondary flow, which in turn acts on thelarge diaphragm to control a larger flow. By seeping this secondary flowthrough a very small valve, the filling process for the two-stage valve,when designed as a microvalve, is substantially slower than the smallvalve actuation speed. A proper design optimizes the tradeoff betweenthe small valves controlling a small, high pressure flow to switch alarge, high pressure flow at the expense of switching time.

[0019] The invention has now been explained with reference to specificembodiments. Other embodiments will be apparent to those of ordinaryskill in the art in view of the foregoing description. It is notintended that this invention be limited except as indicated by theappended claims and their full scope equivalents.

What is claimed is:
 1. A two-stage valve for controlling the flow of gas therethrough from a pressurized gas supply comprising: an upper main body including a cavity therein; a lower main body having at least one pressurized gas supply exhaust outlet passage forming a primary flow path with the pressurized gas supply; a pre-stressed diaphragm sandwiched between said upper and lower main bodies, said pre-stressed diaphragm having one side of a portion thereof in fluidic communication with said cavity, and the opposite side of said portion thereof in fluidic communication with the pressurized gas supply; and pressure control means fluidically coupled to said cavity for controlling the pressure in said cavity to cause said portion of said pre-stressed diaphragm to open the flow of gas from the pressurized gas supply through said primary flow path of said two-stage valve and to cause said portion of said pre-stressed diaphragm to close the flow of gas from the pressurized gas supply through said primary flow path of said two-stage valve.
 2. The two-stage valve of claim 1 wherein said pressure control means comprises: said lower main body having a secondary flow path communicating with the pressurized gas supply, said upper main body having a secondary flow path communicating with said secondary flow path in said lower main body, and communicating with said cavity in said upper main body; a first valve providing (a) an isolating means for isolating the flow of gas from the pressurized gas supply to said cavity in said upper main body, and (b) an opening means for allowing the gas from the pressurized gas supply to flow to said cavity in said upper main body, said upper main body having an exhaust passage for fluidically communicating said cavity with an environment at a pressure lower than the pressure of the pressurized gas supply, a second valve installed in said exhaust passage, said second valve providing an isolating means for fluidically isolating said cavity in said upper main body from the environment, and an opening means for opening said cavity in said upper main body to exhaust to the environment.
 3. The two-stage valve of claim 2 wherein said first valve is installed in one of (a) said secondary flow path in said lower main body, and (b) said secondary flow path in said upper main body.
 4. The two-stage valve of claim 1 wherein said lower main body includes a cavity.
 5. The two-stage valve of claim 4 wherein said lower main body has a boss formed in said cavity of said lower main body, said boss surrounding a hole acting as said inlet primary flow path for the flow of gas from the pressurized gas supply, said hole fluidically coupled to said opposite side of said portion of said pre-stressed diaphragm.
 6. The two-stage valve of claim 5 wherein said boss formed in said cavity of said lower main body is positioned coincident with the center of said cavity of said lower main body. 